Known in the art are ribbon loudspeakers comprising permanent magnets, sound-reproducing ribbons made of an electrically conductive material and disposed in the working gaps between the poles or pole pieces of permanent magnets (U.S. Pat. No. 4,319,096).
High sound reproduction fidelity is provided by ribbon loudspeakers, in which the permanent magnets are arranged along an open loop, forming an open magnetic system. In devices of this type the most natural, noise-free operating mode of the sound-reproducing ribbons is attained due to the fact that rearward radiation is not shielded and each ribbon operates independently. These devices are disadvantageous in that the active element of the sound-reproducing ribbon occupies an insignificant part of the loudspeaker area. Another disadvantage is a small width of the employed sound-reproducing ribbons, which is due to a short uniform magnetic field between the poles of the magnets, and it presents a severe problem in obtaining the desired low-frequency sound intensity.
Known in the art is a ribbon loudspeaker (U.S. Pat. No. 4,027,111), selected as a prior art device comprising permanent magnets, forming an open magnetic system, sound-reproducing ribbons made, for example, in the form of corrugated members of an electrically conductive material, each of which is located in the working gap between the poles of the adjacent permanent magnets. The length of the magnets in this device is equal to 60-70 mm, while the working gap width is 7-10 mm. Thus the total area of the sound ribbons is equal to only 5-12% of the total area of the device. The remaining area is occupied by passive, non-sound-radiating side faces of the permanent magnets, which affects the loudspeaker. Still another disadvantage of the prior art device is a low sound pressure in the low-frequency audio range due to the small width of the sound ribbons, hence the poor-quality of sound reproduction.